Exact Spectral Function of a Tonks-Girardeau Gas in a Lattice.

The single-particle spectral function of a strongly correlated system is an essential ingredient to describe its dynamics and transport properties. We develop a method to evaluate exactly the spectral function for a gas of one-dimensional bosons with infinitely strong repulsions valid for any type of external confinement. Focusing on the case of a lattice confinement, we find that the spectral function displays three main singularity lines. One of them is due uniquely to lattice effects, while the two others correspond to the Lieb-I and Lieb-II modes occurring in a uniform fluid. Differently from the dynamical structure factor, in the spectral function the Lieb-II mode shows a divergence, thus providing a route to probe such mode in experiments with ultracold atoms.

Damping of Josephson Oscillations in Strongly Correlated One-Dimensional Atomic Gases.

We study Josephson oscillations of two strongly correlated one-dimensional bosonic clouds separated by a localized barrier. Using a quantum-Langevin approach and the exact Tonks-Girardeau solution in the impenetrable-boson limit, we determine the dynamical evolution of the particle-number imbalance, displaying an effective damping of the Josephson oscillations which depends on barrier height, interaction strength, and temperature. We show that the damping originates from the quantum and thermal fluctuations intrinsically present in the strongly correlated gas. Because of the density-phase duality of the model, the same results apply to particle-current oscillations in a one-dimensional ring where a weak barrier couples different angular momentum states.

Anderson localization of a Bose-Einstein condensate in a 3D random potential.

We study the effect of Anderson localization on the expansion of a Bose-Einstein condensate, released from a harmonic trap, in a 3D random potential. We use scaling arguments and the self-consistent theory of localization to show that the long-time behavior of the condensate density is controlled by a single parameter equal to the ratio of the mobility edge and the chemical potential of the condensate. We find that the two critical exponents of the localization transition determine the evolution of the condensate density in time and space.

Soluble models of strongly interacting ultracold gas mixtures in tight waveguides.

A Fermi-Bose mapping method is used to determine the exact ground states of several models of mixtures of strongly interacting ultracold gases in tight waveguides, which are generalizations of the Tonks-Girardeau (TG) gas (1D Bose gas with point hard cores) and fermionic Tonks-Girardeau (FTG) gas (1D spin-aligned Fermi gas with infinitely strong zero-range attractions). We detail the case of a Bose-Fermi mixture with TG boson-boson (BB) and boson-fermion (BF) interactions. Exact results are given for density profiles in a harmonic trap, single-particle density matrices, momentum distributions, and density-density correlations. Since the ground state is highly degenerate, we analyze the splitting of the ground manifold for large but finite BB and BF repulsions.

Bosonization, pairing, and superconductivity of the fermionic Tonks-Girardeau gas.

We determine some exact static and time-dependent properties of the fermionic Tonks-Girardeau (FTG) gas, a spin-aligned one-dimensional Fermi gas with infinitely strongly attractive zero-range odd-wave interactions. We show that its two-particle reduced density matrix exhibits superconductive off-diagonal long-range order, and on a ring an FTG gas with an even number of atoms has a highly degenerate ground state with quantization of Coriolis rotational flux and high sensitivity to rotation and to external fields and accelerations. For a gas initially under harmonic confinement, we show that during an expansion the momentum distribution undergoes a "dynamical bosonization," approaching that of an ideal Bose gas without violating the Pauli exclusion principle.

Collective modes and ballistic expansion of a fermi gas in the BCS-BEC crossover.

We evaluate the frequencies of collective modes and the anisotropic expansion rate of a harmonically trapped Fermi superfluid at varying coupling strengths across a Feshbach resonance driving a BCS-BEC crossover. The equations of motion for the superfluid are obtained from a microscopic mean-field expression for the compressibility and are solved within a scaling ansatz. Our results confirm nonmonotonic behavior in the crossover region and are in quantitative agreement with current measurements of the transverse breathing mode by Kinast et al. [Phys. Rev. Lett. 92, 150402 (2004)]] and of the axial breathing mode by Bartenstein et al. [Phys. Rev. Lett. 92, 203201 (2004)]].

Exact particle and kinetic-energy densities for one-dimensional confined gases of noninteracting fermions.

We propose a new method for the evaluation of the particle density and kinetic pressure profiles in inhomogeneous one-dimensional systems of noninteracting fermions, and apply it to harmonically confined systems of up to N = 1000 fermions. The method invokes a Green's function operator in coordinate space, which is handled by techniques originally developed for the calculation of the density of single-particle states from Green's functions in the energy domain. In contrast to the Thomas-Fermi approximation, the exact profiles show negative local pressure in the tails and a prominent shell structure which may become accessible to observation in magnetically trapped gases of fermionic alkali atoms.

Microbiological research on soft drinks: discolouring of natural-flavoured products.

The results of experiments testing the effects of yeasts, sunlight, and temperature on the food dyes tartrazine, ponceau 4R, indigotin and azorubin (used for colouring ginger soft drink) are reported. Light was found to exert a greater influence than heat, and yeasts growth hastened colour degradation. Yeasts assimilated to varying extent the colouring compounds and, when failing to do it, showed a certain power of adsorption by the no longer viable cells.

[Results of some experiences on modern techniques of vinification of red grapes]. / Risultati di alcune esperienze su moderne tecniche di vinificazione in rosso

The results of experiences carryed out at the "Istituto di Industrie Agrarie" of the University of Bologna in the last five years, applying the techniques of vinification by carbonic maceration (CM) and by heat treatment of the crushed in the production of Emilia-Romagna wines, are reported. In particular, the evolution of the main organic constituents during anaerobic conditioning of grapes, the possibility of applying the CM to Sangiovese, Merlot and Canina grapes, the different variations of the CM technique, that is, CM followed by information with skins, the rifermentation of wines produced by traditional method with 10-20% of grape juice obtained by CM, the influence of CM on aging of barbera wine, some laboratory tests to explain the mechanism that regulate same interaction phenomena during the "intracellular fermentation", are discussed. The results of technique of heat treatment of the crushed, in the vinification of Sangiovese grapes, in a pilot plant, are exposed. Finally, the effects of some parameters (treatment of the crushed integral or partially dripped, heating temperature, rest time, sulphur dioxide employ, etc.) on the chemical characteristics and on the organoleptic quality, are estimated.

[The determination of lead in musts, wines and vinegars (author's transl)]. / Determinazione del piombo nei mosti, nei vini e negli aceti

A method is described for the determination of lead in musts, wines and vinegars by atomic absorption spectroscopy. The method, already proposed as an official method both in Italy and at the O.I.V., gives sufficiently accurate and reproducible results and is particularly suitable for routine analysis. It has been tested on 120 white and red italian wines and has shown that lead pollution in wines has not reached dangerous limits.

[Chemical characteristics of "artificial wines" (author's transl)]. / Caratteristiche chimiche dei "vini artificiali"

A wide investigation has been carried out in order to evidenciate the differences of composition between "artificial wines" and genuine wines. "Artificial wines" have been produced by fermentation of mixtures of different amounts of wine making by-products (less, pomaces and press-wines), water and sucrose. The results showed, in particular, that "artificial wines" have a very low content of both malic acid and proline and a high content of nitrates. Significant differences have been also found in the content of polyphenols, alkaline and alkaline earth metals and citric acid.